Subnet Calculator

What this result means

A subnet divides an IPv4 address into network and host portions. The prefix length identifies network bits; the remaining bits determine the size of the address block.

Understanding subnet calculations

A subnet calculator turns an IPv4 address and prefix into the boundaries that routers and administrators use. For example, 192.168.1.10/24 belongs to the 192.168.1.0 network, with 256 total addresses. The /24 means the first 24 bits identify the network and the final eight bits identify positions inside that network.

The subnet mask is another way of writing the same boundary. A /24 is 255.255.255.0: its one bits mark the network portion, while the zero bits mark host positions. A wildcard mask reverses that view and is useful in some routing and firewall configurations. The network address identifies the block, and the broadcast address reaches every address in a traditional IPv4 subnet.

Usable-host counts need context. Most prefixes from /0 through /30 reserve the network and broadcast addresses, leaving two fewer traditional host addresses. A /31 is commonly used for point-to-point links and has two usable addresses under RFC 3021. A /32 represents one host route, so it has no traditional host range to display.

Class A, B, and C labels are shown only as legacy context. Modern networks use classless CIDR prefixes, so the prefix—not a class label—determines the actual network size and mask. Private ranges calculate exactly like public ranges; the calculator does not contact an external service or look up the address.